Preheat the oven: Preheat your oven to 375°F (190°C). Grease or line a 9-inch baking dish with parchment paper.

1. Prepare the berry filling: In a large bowl, combine the strawberries, blueberries, sugar, cornstarch, lemon juice, and vanilla extract. Toss until the berries are evenly coated and the mixture begins to release juice. Transfer the berry mixture into the prepared baking dish and spread it out evenly.
2. Prepare the mascarpone layer: In a medium bowl, whisk together the mascarpone cheese, powdered sugar, and vanilla extract until smooth and creamy. Spoon dollops of the mascarpone mixture over the berry filling. Don’t worry if it doesn’t cover the berries completely; it will melt into the filling as it bakes.
3. Prepare the biscuit topping: In a large bowl, whisk together the flour, sugar, baking powder, and salt. Add the cold, cubed butter and use a pastry cutter or your fingers to work the butter into the dry ingredients until the mixture resembles coarse crumbs. Add the heavy cream and vanilla extract, and stir until just combined. The dough will be slightly sticky.
4. Assemble the cobbler: Drop spoonfuls of the biscuit dough over the berry and mascarpone mixture, covering as much of the surface as possible. It’s okay if some of the berries peek through.
5. Bake: Bake the cobbler in the preheated oven for 40-45 minutes, or until the biscuit topping is golden brown and the berry filling is bubbly.
6. Cool and serve: Allow the cobbler to cool slightly before serving. For extra indulgence, serve it with a scoop of vanilla ice cream or a dollop of whipped cream.